Referring to FIG. 1, a prior art elastic cushion 5 is illustrated. The method for forming ventilation holes 21 on an elastic cushion 2 is illustrated. The elastic cushion 2 in the prior art is punched by a plurality of pins continuously so as to formed a plurality of holes which may have smaller sizes (referring to FIG. 1) or larger sizes (referring to FIG. 2). In this prior art, under considering the problem of removing the waste from punching the holes, the size of the holes can not be reduced to a desired value and the density of holes is low.
Although the prior art cushion 2 drains out some wastes so that the elastic cushion 2 is light, the ventilation holes 21 are distributed on the cushion selectively on some part. Thus, the ventilation is bad at some parts lack of ventilation holes. Moreover, the holes will cause that the support of the elastic cushion 2 is not good so that the surface of the elastic cushion 2 will not smooth as being used for a long time.
To solve above mentioned defect in the prior art, in another design, as shown in FIGS. 3 and 3A, corrosive is coated on the surface of an elastic cushion 3 so that the surface is corroded and thus the surface will form a plurality of ventilation holes 31. Although the elastic cushion 3 may vent air in wholly surface, in this prior art, the ventilation holes are distributed statistically and thus not uniform. Moreover, some corrosive agents will leave on the surface of the elastic cushion 3 so that the specific gravity of the elastic cushion 3 will increase.
Moreover, this prior art way is too high. Thereby, the ventilation holes 31 will cause that the surface of the elastic cushion 3 is not flat so that the gluing or adhering operations on the surface of the elastic cushion 3 is not strong and therefore, the strength of the structure is not preferred.